The work of G. R. Gibson and M. B. Roberfroid has set out the concept of food ingredients known as “prebiotic”. These are ingredients that are not digestible, but that serve selectively to stimulate the growth and/or the activity of a specific bacterium or of a small number of species of colon bacteria, thus improving the health of the consumer. In order to be “prebiotic”, the food ingredient must satisfy the following conditions. It must not be hydrolyzed or absorbed in the upper portion of the digestive tract. It must constitute a selective substrate for the specific bacteria or a small number of favorable colon bacteria, whose development and/or metabolism is stimulated. Consequently, it must be capable of favorably modifying the composition of the colon microflora. Finally, it must induce systemic effects that stimulate health of the consumer.
Until now, the only food ingredients that have been recognized and used as satisfying the above conditions are fructanes or oligofructoses. With reference to the 1995 article by Gibson and Roberfroid, the term “fructo oligosaccharide” (FOS) designates oligofructoses that are polymerized up to degree 9 at most, and the term “inulin” designates an oligofructose having a higher degree of polymerization, lying in the range 10 to 60, and on average 12.
However, in the literature, the generic term “inulin” is used frequently to designate inulin proper and also fructo oligosaccharides (FOS). It is in this generic sense that the term “inulin” is used in the present specification.
Carbohydrates are not digestible in the upper portion of the tractus; they are not subject to the enzymatic action of amylases, saccharases, maltases amongst others. Thus, inulin and FOS pass from the ileum to the colon without being absorbed, and they are considered in this respect as constituting alimentary fibers. However, although they are not metabolized by digestive enzymes, they nevertheless present calorific value. Intestinal microflora can metabolize them into short-chain fatty acids (aliphatic organic acids) and into lactate (organic acid). The calorific value of inulin and of fructo oligosaccharides (FOS) lies in the range 4.2 kilojoules per gram (kj/g) to 6.3 kj/g, i.e. in the range 1 kilocalorie per gram (kcal/g) to 1.5 kcal/g.
Furthermore, the bifidostimulating effect has been demonstrated by experiments both in vitro and in vivo for fructo oligosaccharides and for inulin. In particular, experiments carried out by the biomedical sciences department of the Tokyo Agriculture Faculty have shown an improvement in fecal microflora after administering 8 grams (g) of fructo oligosaccharides for 2 weeks. The number of bifidobacteria in stools was multiplied by ten. The mean pH of the stools was lowered by 0.3 and the authors observed an improvement in lipid metabolism. It has thus been shown that so-called “prebiotic” ingredients are effective in changing the composition of intestinal microflora, such that favorable bacteria predominate over species that are potentially dangerous.
It is known that inulin is one of the components of chicory, possibly representing as much as 70% of the dry matter of chicory root. This root is indeed used for extracting inulin. However, concerning the use of chicory as a food ingredient, the conventional method comprises a plurality of steps of dehydration, roasting, extraction, and atomization, during which the inulin content decreases and can become zero. More precisely, the inulin becomes degraded into fructose, particularly under the combined action of temperature and moisture. That is what makes it possible to obtain the particular taste, aroma, flavor, and color of conventional soluble roasted chicory which is used a food ingredient.
According to the Applicant, the soluble roasted chicory obtained by the conventional method—referred to below as “conventional” chicory—has an inulin content of about 18% to 19%, and in any case less than 20%.